Grids & Datums SULTANATE OF OMAN by Clifford J. Mugnier, C.P., C.M.S.

The Persian Gulf lies between two of the major breadbaskets of the The only known classical geodetic datum in Oman is the Fahud ancient world, the Tigris-Euphrates area (Mesopotamia, meaning Geodetic Datum of 1954, which was established by the Iraq Petro- “between the rivers”) in present-day Iraq and the Nile Valley in Egypt. leum Corporation (IPC) for the Petroleum Development Oman (PDO) Mesopotamia, a part of the area known as the Fertile Crescent, was operation. Beginning in 1964, Hunting Surveys, Ltd., established an important not only for food production but also for connecting East extensive control network based on the Fahud Datum of 1954, and to West. Mesopotamia became the linchpin of ancient international this enterprise took over eight years to develop. Although the work trade. The fertile soil between the Tigris and the Euphrates produced was performed to a 3rd Order geodetic accuracy specification, the a large surplus of food; however, it did not support forests to produce operational demands of a production oil field precluded the rigor- the timber necessary to build permanent structures. The region also ous adjustment of the network. As a result, the classical network lacked the mineral resources to make metals. Accordingly, the early retained a number of relatively high distortions of up to 10 meters inhabitants of Mesopotamia were forced to go abroad and trade their in magnitude for horizontal coordinate positions and up to 5 meters food for other raw materials. They found copper at Magan, an ancient in elevation! A major Doppler satellite campaign was observed be- city that lay somewhere in the contemporary state of Oman and, via tween September 1983 and August 1984. During this period, 106 Magan, traded with people in the Indus Valley for lumber and other existing stations in the Fahud Datum of 1954 network were occupied finished goods. The people of Magan were both middlemen and and observed. Subsequent to the initial period of survey work in suppliers because the city was a source of copper as well as a transit Oman, all survey stations to the north of latitude 22º were given the point for Indian trade. Over time, other cities developed that were prefix “NO,” and those to the south the prefix “SO.” This numbering exclusively entrepôts, or commercial way stations. One of the best system was later extended into the province of Dhofar, where the known of these cities was Dilmun. Dilmun probably lay on what is now prefix “D” is used instead. The Fahud Datum of 1954 uses the Clarke the island state of Bahrain. Excavations on the island reveal rich burial 1880 as its ellipsoid of reference where: a = 6,378,300.782 m, and 1 mounds from the Dilmun period (ca. 4000 to 2000 B.C.). The area that /f = 293.4663077. The origin point of the Fahud Datum is near station constitutes the present-day Persian Gulf states was on the immediate “NO68-024” where the Astronomical Latitude, Φo = 22º 17’ 31.182” periphery of the rise of Islam. In A.D. 610, Muhammad — a merchant North, and the Astronomical Longitude, Λo = 56º 29’ 18.820” East of the Hashemite branch of the ruling Quraysh tribe in the Arabian of Greenwich. The original astronomical origin point at F.N. Fort (sta- town of Mecca — began to preach the first of a series of revelations tion “F1” with defining azimuth to station “F2” of the baseline) has that Muslims believe was granted him by God … Shia Muslims hold been destroyed. The baseline was located on a gravel plain on the the fundamental beliefs of other Muslims. In addition to these tenets, southern side of an airstrip constructed for the survey. A total of 32 however, Shia believe in the imamate, which is the distinctive institu- stations were triangulated in Fahud, including F15 and F5, and 15 tion of Shia Islam. The term Kharijites also became a designation for stations were triangulated in Natih, including N1. Original coordi- Muslims who refused to compromise with those who differed from nates of the triangulation were published on the WWII Trucial Coast/ them. Their actions caused the Sunni community to consider them Qatar Grid on the Cassini-Soldner projection. The Central Meridian, assassins. In the eighth century, some Kharijites began to moderate λ o = +50° 45’ 41” E, the False Northing Latitude of Origin, their position. Leaders arose who suppressed the fanatical political (ϕFN) = 25° 22’ 56.5” N, and both the False Eastings and False Northings element in Kharijite belief and discouraged their followers from taking are 100 km. Of course, the scale factor at origin by definition is equal up arms against Islam’s official leader. Kharijite leaders emphasized to unity. Also used in the region was the Mecca-Muscat Zone on the instead the special benefits that Kharijites might receive from living in Lambert Conical Orthomorphic projection where the Central Meridian, a small community that held high standards for personal conduct and λo = 45° East of Greenwich, the Latitude of Origin, ϕo = 23° N, a Scale spiritual values. One of these religious leaders, or imams, was Abd Factor at Origin, mo = 0.99907, and a False Easting, F.E. = 1,000 km Allah ibn Ibad, whose followers founded communities in parts of Africa at the Central Meridian. The Oman Transverse Mercator projection and southern Arabia. Some of Abd Allah’s followers, known as Ibadis, has a Central Meridian, λo = 54° East of Greenwich, a Scale Factor at became the leaders of Oman” (Library of Congress Country Studies). Origin, mo = 0.9997, and a False Easting, F.E. = 500 km at the Central The Sultanate is bordered on the west by Saudi Arabia (676 Meridian. Notice the curious similarity in the digits used for the Scale km), United Arab Emirates (410 km) (PE&RS, February 2001), Ye- Factor at Origin values for the Mecca-Muscat Lambert zone and the men (288 km) (PE&RS, August 2003), and on the north, east, Oman Transverse Mercator belt — I’ll bet that’s not a coincidence. and south by the Gulf of Oman and the Arabian Sea (2,092 km). “The astronomical observations were approximately located on a The terrain is comprised of a vast central desert plain with rug- 25 km grid in order to provide control for relative gravity surveys. Six ged mountains in the north and south. The lowest point is the to ten pairs of circum-meridian observations and 8-13 pairs of time Arabian Sea (0 m), and the highest point is Jabal Shams (2,980 m). stars were generally observed for the astrofixes. By 1957, triangulation continued on page 230 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING March 2007 229 continued from page 229 networks had been established in the Buraimi area, the Duqm/Huqf area, and in the vicinity of Fahud covering over 2 degrees of latitude between Dhank and Nihayda. After the completion of the initial survey, the IPC Photo survey section in Tripoli, Lebanon used February 1953 aer- ial photographs to produce a Fahud Topographical Map at a scale of 1:25,000 on the UTM grid. A subsequent geo- logical map was cast on the Trucial Coast grid in July 1956. “During 1964, a survey was conducted by the British Army Directorate of Military Survey (DMS), which in- volved a cantilevered Telurometer traverse from Dubai in the United Arab Emirates through Buraimi to Fahud (Series 13B). The traverse, to extend available control, was car- ried out by 13 Field Survey Squadron, during April-May 1964. In 1964, Hunting Surveys, Ltd. was contracted by PDO to install new control by Telurometer traversing for mapping and oil exploration purposes. The specification called for station intervals of about 20 km, with azimuth stations; and at each station, for 3 sets of simultaneous re- ciprocal vertical angles. Distances were to be observed in both forward and reverse directions with agreement bet- ter than 1/50,000. Polaris azimuths were to be observed at 100 km intervals. (This was amended to 60 km in later years). Closure between azimuths was specified to be less than 2” per station” (M.H.B. Jensen, December 1984). The original Fahud Height Datum was based on reciprocal trigonometric heighting from a single MSL determination at Mina al Fahal (formerly known as Saih al Maleh) in Muscat. Station NO68-024 had an orthometric height of 323.50 m above mean sea level at Mina al Fahal. According to the Ordnance Survey of Great Britain: “PDO Height Datum of 1993 - Misclosure between Muscat and Salalah less than .5 meters with dif- ferences from of up to 5 meters from old Fahud Datum. The PHD93 adjustment was initially known as the Spine (sic – Ed). Supercedes Fahud Vertical Datum from 1993.” The transformation f r o m W G S 8 4 D a t u m to PDO Survey Datum 1993 listed by Wilfred of Medco Energy in 2005 is: ∆X = +180.624 m, ∆Y = +225.516 m, ∆Z = –173.919 m, δS = –16.71006 ppm,

Rx = –0.80970”, R y = –1.89755”, Rz = +8.33604”. No information was offered regarding transforma- tion accuracy nor the sense of the coordinate system rotations, but fortunately a test point was provided where: PSD93 (Clarke 1880) ϕ = 20º 20’ 56.967” North, λ = 56º 31’ 15.467” East and WGS84 ϕ = 20º 20’ 58.495” North, λ = 56º 31’ 25.456” East. While researching Oman, I noticed that the Honorable Gary A. Grappo is currently the United States Ambassador to the Sultanate of Oman. Ambassador Grappo holds a Masters Degree in Geodesy from Purdue University.  The contents of this column reflect the views of the author, who is responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the American Society for Photo- grammetry and Remote Sensing and/or the Louisiana State University Center for GeoInformatics (C4G).

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